BAMBOO FIBER AND BAGASSE FIBER REINFORCED FUNCTIONALIZED THERMOPLASTIC ELASTOMER COMPOSITES

Abstract

Thermoplastic elastomers (TPEs) are increasingly being used for many applications as their relatively higher cost compared to polyolefin is justified in applications where these materials perform better because of their higher properties and low-cost processing. Reinforced TPEs are expected to replace TPEs in several applications, including, interior and exterior components of automobiles. Eco-friendly, biodegradable, and low cost natural fibers with good properties are substituting inorganic and synthetic fibers as reinforcement for polymer composites. Natural fiber / polymer composites offer synergistic properties of the reinforcing natural fibers and the matrix polymer and also offer techno-economic and environmental advantages. However, polar and hydrophilic natural fibers have poor compatibility with non-polar hydrophobic polymer matrix in a natural fiber / polymer composite that results in poor fiber / matrix interfacial adhesion and adversely affects the mechanical properties of the composite. Three processes have been developed to manufacture natural fiber / polymer composites with improved fiber /matrix interfacial adhesion: (i) Natural Fiber Treatment Process, (ii) Compatibilizer Process and (iii) Palsule Process, that uses a chemically functionalized polymer as the matrix that develops adhesion with natural fibers by chemical reactions between functional groups of the functionalized polymer matrix and of the natural fiber. Several natural fiber reinforced chemically functionalized polyolefin composites have been developed by Palsule process; and this study is an attempt to extend Palsule process to the natural fiber reinforced chemically functionalized thermoplastic elastomers composites. Accordingly, chemically functionalized ethylene propylene rubber (CF-EPR) and chemically functionalized styrene ethylene butylene styrene (CF-SEBS) have been used as the matrix and bagasse fibers (BGSF) and recycled bamboo fibers (R-BMBF), that have almost similar holocellulose (cellulose and hemi-cellulose) (approx. 70%) contents have been selected as the reinforcing natural fibers. This study develops the following four natural fibers reinforced chemically functionalized thermoplastic elastomer composites: • Recycled bamboo fiber reinforced chemically functionalized ethylene propylene rubber composites: R-BMBF/CF-EPR Composites. • Bagasse fiber reinforced chemically functionalized ethylene propylene rubber composites: BGSF/CF-EPR Composites. Recycled bamboo fiber reinforced chemically functionalized styrene ethylene butylene styrene composites: R-BMBF/CF-SEBS Composites. • Bagasse fiber reinforced chemically functionalized styrene ethylene butylene styrene composites: BGSF/CF-SEBS Composites. Three compositions, i.e., 15/85, 25/ 75 and 35/65 of each of the R-BMBF/CF-EPR, BGSF/CFEPR R-BMBF/CF-SEBS and BGSF/CF-SEBS composites, have been processed by twin screw extrusion followed by injection moulding of the extrudates to obtain the samples for testing and characterizations required as per the ASTM standards. The formation of all the composites has been established by demonstrating their higher mechanical properties than their respective matrix and increase in these properties with the increasing respective reinforcing natural fiber contents in them. Dynamic mechanical thermal properties of all the composites have been evaluated and all the composites show higher storage modulus and higher loss modulus than that of the respective matrix and these increase with increasing respective reinforcing fiber contents in them. Morphology of all the four composites, established by FE-SEM micrographs, shows the respective fibers deeply embedded and fully covered by the respective matrix without any fiber pullout and establishes good fiber/matrix interfacial adhesion in all the composites. The chemical interactions imparting this fiber/matrix interfacial adhesion has been established by the FTIR spectra of all the composites that establishes esterification and hydrogen bonding between functional groups of the respective functionalized polymer matrix and of the respective natural fiber. Ester and hydrogen bonds impart good fiber/matrix interfacial adhesion in all the four composites. Thermal degradation of all the four composites initiates at a lower temperature than that of the respective polymer matrix but at a higher temperature than that of the respective reinforcing natural fiber and the all the composites show thermal stability in-between those of respective reinforcing natural fiber and the respective polymer matrix. Water absorption and thickness swelling by all the four composites increase with increasing contents of the respective reinforcing fibers in the composites. Tensile properties of water absorbed wet composites are lower than those of the respective dry composites but are higher than their respective dry and wet matrix material. All the R-BMBF/CF-EPR, BGSF/CF-EPR R-BMBF/CF-SEBS and BGSF/CF-SEBS composites are eco-friendly with several potential applications including furniture and some components of kitchen, automobiles and building materials.